package leetcode;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * 三数之和，排序加双指针
 */
public class SumOfThreeNums {
    public static void main(String[] args) {
        System.out.println(threeSum(new int[]{-1,0,1,2,-1,-4}) );
    }
    public static List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        Arrays.sort(nums);
        for (int i = 0; i < nums.length; i++) {
            if(nums[i] > 0)
                break;
            if(i > 0 && nums[i] == nums[i - 1])
                continue;
            int l = i + 1, r = nums.length - 1;
            while(l < r)
            {
                int sum = nums[i] + nums[l] + nums[r];
                if(sum == 0)
                {
                    List<Integer> list = new ArrayList<>();
                    list.add(nums[i]);
                    list.add(nums[l]);
                    list.add(nums[r]);
                    result.add(list);
                    while(l < r && nums[l] == nums[l + 1])
                        l++;
                    while(l < r && nums[r] == nums[r - 1])
                        r--;
                    l++;
                    r--;
                }
                if(sum > 0)
                    r--;
                if(sum < 0)
                    l++;
            }
        }
        return result;
    }
}
